Among device or apparatuses to be loaded on a vehicle, there are many that are controlled by a control value determined on the basis of plural input signals. Such devices and apparatuses may include a fuel injection system, a spark control device, a control apparatus for an automatic transmission, an attenuation control device for a suspension, an anti-brake lock device, a slip (traction) control apparatus, and an automatic drive apparatus. Recently, there is an increasing tendency that the number of sensors to be employed for control of the device or apparatus is increased, thus leading to an increase in the number of input signals, in order to control these devices and apparatuses in an optimum manner. As input signals may be used the number of engine revolutions, an engine load, a vehicle speed, an intake air amount, an intake air temperature, a battery voltage, an engine coolant temperature, an intake air density, a gear shift position, a slip state of a road surface, a loadage, an acceleration or deceleration speed, a road inclination, the number of wheel revolutions, a steered angle of a steering wheel, transverse G and so on. Such input signals as being of the manual type can also be used.
A conventional system for determination of a control value for a device to be loaded on a vehicle using plural input signals is disclosed in Japanese Patent Publication (laid-open) No. 159,928/1979 that is directed to a correction of a basic speed mode pattern of an automatic transmission on the basis of plural input signals. In determining a control value for this correction, the correction is made by adding plural correction coefficients obtained for signal values from the sensors. On top of that, a control value can also be obtained by multiplying correction coefficients obtained for input signal values by each other.
As the number of input signals as a basis for determining a control value increases, it becomes more difficult to give an optimum control value by way of addition or multiplication as have been used in conventional techniques. An increase in the number of the input signals increases conditions for combinations of the signal values in arithmetic progression. Accordingly, with conditions for all possible combinations taken into account, the formulation of each of the correction coefficients for all the combinations might destroy a whole balance if a correction characteristic for a certain signal value would be modified or might give an inappropriately final control value that could not be predicted in advance.
Furthermore, if an optimum control value could be obtained for all the possible combination conditions, a tremendous amount of laborious experiments should be repeated until such conditions have been set. In particular, work for confirmation and modification made by a great number of driving experiments should be so tremendously laborious because the optimum control value is required to be suited for the feeling or perception of an operator. In addition, characteristics for obtaining correction coefficients to be set for each of the input signals should be rendered so complex and delicate that a great burden may be given a control system in memorizing the characteristics.